Electric projection lamp



July 19, 1949. L, G, LHGHTON 2,476,671

ELECTRIC PROJECTION LAMP Filed Sept. 28, 1945 FIG. 1 28 I 2/ 29 ir f/ 22 26 //|/////N/// J//////./////-//5 INVENTOR LEROY G. LEIGHTON B MW HIS ATTDRNEY Patented July 19, 1949 ELECTRIC PROJECTION LAMP Leroy c. Iieighton; *01eveland,-0hio, assign:- to.

General :Electric Oompany, :a corporation of New York Application September 28,1945, Serial No. stares screens (01. Md-413 invention relates to electric lamps and more particularly to such lamps having a prefoous'base for use in picture projection apparatus.

The principal object of my invention is to provide an electric projection lamp having *a prefocus base which positions the lamp more accurately than present bases and in which "the electrical connections to the lamp terminals may be made independently of the prefocusin'g means on the baseto simplify the structure of the socket for the lamp. Another object of my invention is to provide a pro-focus base for an electric lamp which facilitates cooling of the lamp by the ventilating systemior the lamp house of a projection apparatus. A further obfrect of my invention :"is to provide an electriclamp having a prefocus base and a socket therefor of simple structure and which socket maybe made integral with the lamp house of a picture 'proiection apparatus. Further obiects and advantages of the invention will appear from the following detailed description of a species thereof and from the appended claims.

In the drawing accompanying and forming part of this specification an embodiment of my invention is shown in which Fig. 1 is a side-elevational, fragmentary, partly sectional view of -a lamp chamber and showing in side elevation the lamp mounted therein: Fig. '2 is a bottom plan view of the cover of the chamber shown "in Fig. 1'; Fig. 3 is "a perspective view of the base-end of the lamp shown in Fig. 1 as seen irom below, and Fig. *4 is a similar view of the base end of the lamp as seen from above.

\ The lamp 1 shown in Figs. '1, '3 and 4 is the same as the incandescent projection lamps for base-up mounting well known in commerce except for the construction of the prefocus base 2 which has two metal contact terminals 3 and 4 on its exposed end (Fig. 4') and a flange comprising a ring 5 attached to the outer metal shell ,5 of the base 2 which shell is electrically insulated from contacts 3 and 4; The ring 5 is substantially larger in diameter than the tubular bulb 1 of the lamp 1 and is attached to the lamp base 2 by inwardly extending arms 8 the inner ends 9 of which are turned toward the terminal end of the base 2 and soldered, welded or brazed to the metal shell G-of the base L The ring 5, arms 8 and base 2 thus define vent openings 32 whichextend radially inward of the pref-causing flange to a point within the projected confines of that portion of the bulb wall adjacent the base 2. The surface l of the ring facing away from the base end of the lamp I has three bosses ll spaced approximately degreesapart and adjacent its outer edge. The bosses 'H provide a three point support Tor the lamp I and may be accurately shaped and dimensioned to hold the lamp filament (not shown) in proper position at focus of the optical system of the projection apparatus when the lamp 1 is mounted in the chamber-show in Fig. '1. The ring 5 may of course be omitted and the ends of arms 8 'provideo with bosses ll or spaced lugs or wings may be used on the base to constitute a transversely extending projection to serve the same purpose as the flange.

The lamp chamber "ll of Fig. 1- comprises a tubular metal casing the inner surface of'whic'h is formed with a circular recess l4 which fits the ring 5 and provides an annular shoulder 15 for supporting the ring *5 and the lamp '1. A cylindrical pin "15 is mounted in a cavity in the wall of the housing 13 andextcnds into "the recess '14 to engage the semi-circular slot 11 in the ring 5 to hold the ring 5 and the lamp l against rotation inth'e casing 13. The slot I1 is accurately located with respect toth'c lamp filament.

The lamp chamber also has a top l8 which is hinged at 19 to the casing id-and provided with a catch 20 for releasably looking it with the casing 13. The top "[8 may be made of metal and has secured thereto a block 21 of insulating material carrying a pair of spaced spring contacts '22 and 23 for engaging the contacts '3 and l or the lamp I. When the cover I8 is closed the spring contacts 22 and '23 press the ring 5 firmly against the shoulder lsto hold the lamp filament, which is supported-adlacent the lower end or the envelope '1 by wires 24 and 25 electrically connected to base contacts 3 and A, improper position at the focus of theapparatus. The contacts H -and 23 are provided with insulated current leading-in wires 26 and 21 which pass "through openings in the wall of the cover F8 for connection toan electric power source for the "lamp 1. Conventional enclosed switch means mot shown) actuated by. the cover l8 may be provided as a safety measure to break automatically the circuit "including wires "26 and 21 while "the cover isin its opened position.

The cover has vents 28 at its top through which may pass cooling air forced through the lamp house of the projector by the usual fan arrangement (not shown). The cooling air may how upward in casing 13 past "the lamp *1 through the vents defined by the arms 8, the ring 5 and the base 6 and thence out of the vents 28 in the cover ID to the outer atmosphere. An opaque 3 disc 29 for intercepting stray light is supported over the vents 28 by a stud 30 and bolt 3| as shown in Fig. 1.

The extension of the flange vent openings 32 radially inward of the flange to a point at least approximately within the projected confines of that portion of the bulb wall adjacent the base eliminates any possibility of dead air spaces or pockets of trapped heated air forming at the upper end of the glass bulb in the corner that otherwise would be formed between the prefocusing flange and the bulb wall. This then assures the glass bulb being intimately contacted and scrubbed or washed by the cooling air through-. out its entire length and most important at its upper or based end where the glass gets the hottest during the operation of thelamp.

In placing a lamp I in the lamp house the catch 20 is released and the cover 18 turned 180 degrees on its hinge l9 to give access to the interior of the casing 13. The lamp 1 is then inserted base end up in the casing 13 with the slot I? in the ring 5 properly indexed with the pin l6 and the bosses H resting against the shoulder l5 to hold the lamp filament in proper position at the focus of the light projecting device on which the chamber 12 is mounted. The cover I8 is then returned to and latched in its closed position with its contacts 22 and 23 engaging base contacts 4 and 3, respectively, and the lamp I may then be energized. Lamp replacement may be readily and speedily accomplished in the same manner.

Since the casing I3 and its cover 18 are at ground potential the socket I 2 may be made integral with the lamp housing which is usually made of metal- This is not possible with the usual prefocus bases in which the baseshell conducts power. The metal ring 5,, which acts solely as a support for properly positioning the lamp I and is not included in the lamp circuit, being substantially larger in diameter than similar members used heretofore minimizes the eiiect of inequalities on the shoulder IS on the position of the lamp filament. I prefer to use a ring of approximately 2 /I; inches in diameter with a tubular lamp bulb of approximately 1%; to 1 inches in diameter. v

What I claim as new and desire to secure by Letters Patent of the United States is: 1

1. The combination of a lamp comprising a bulb having a light source therein and a base having insulated contacts on its bottom and a flange comprising a ring substantially larger in diameter than said bulb and secured to said base in predetermined relation to said source by spaced arms, and a chamber enclosing said lampand having a shoulder for engaging said ring to support said lamp in base-up-position with the bulb in spaced relation to the inner wall of the chamber, said ring defining with said arms and said basetopenings through the flange providing vents for the passage of cooling air through the chamber past the lamp, said chamber having a cover provided with electric spring contacts for engaging said base contacts and vents for the passage of cooling air out from the chamber.

2. An electric projection lamp comprising a bulb having a base attached thereto and containing a light source, and a transversely extending annular flange surrounding and accurately located and securedon said base with respect to said source and the outermost portion of which is adapted to engage with a socket, said flange being of appreciably larger diameter than said bulb and comprising an outer continuous ring portion spaced from the base beyond the projected confines of that portion of the bulb outer wall surface adjacent the base by an openwork inner portion extending radially inward of the flange to a point at least approximately within the projected confines of that portion of the bulb outer wall surface adjacent the base, the openings of the said openwork inner portion of the flange constituting the greater part of the said irmer portion of the flange to thereby serve as vents for passage of cooling air therethrough longitudinally of the lamp and in intimate contact with the full length of the bulb.

3. An electric projection lamp comprising a bulb having a base attached thereto and containing a light source, and a transversely extending flange surrounding and accurately located on said base with respect to said source, said flange comprising an outer ring portion secured to said base by inwardly extending spaced arms defining with said ring and said base openings constituting the greater part of the inner portion of the flange and extending radially inward of the flange to a point at least approximately within the projected confines of that portion of the bulb outer wall surface adjacent the base to thereby serve as vents for passage of cooling air therethrough longitudinally of the lamp and in intimate contact with the full length of the bulb, said ring being substantially larger in diameter than said bulb and providing a seating shoulder for accurately locating the lamp in a socket.

4. The combination of a lamp comprising a bulb having a light source therein and a base having a transversely extending flange comprising a ring substantially larger in diameter than said bulb and surrounding said base and secured thereto by inwardly extending spaced arms, and a chamber enclosing said lamp and having a shoulder for engaging said ring and holding said bulb in spaced relation to the inner wall of the chamber, said ring defining with the said arms and said base openings through the flange and extending radially inward thereof to a point at least approximately within the projected confines of that portion of the bulb outer wall surface adjacent the base to thereby provide vents for the passage of cooling air through the chamber past the lamp and in intimate contact with the full length of the bulb thereof.

LEROY G. LEIGHTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS France 1 1939 

